Why Measured Data Matters

Good decisions are driven by good data. This starts with collecting the right kind of data to inform your project.

Aggregated data has its place, but it’s not a one-size-fits-all approach. For example, when you need to evaluate specific patterns on an arterial roadway, you can’t make decisions based on aggregated estimates; you need detailed measured data.

Read on for an explanation of those two terms, and why we encourage our customers to look for raw, high-resolution measured data to calculate arterial performance measures.

Aggregated Data: Available and Scalable

Between apps, cell towers, and other GPS devices, probe data is widespread. Probe data is excellent for planning studies. It’s easy to deploy, easy to get ahold of, and comes in a packaged form that’s ready for you to use. Data is aggregated and approximated by a third party, which makes it scalable for larger planning studies examining high-level patterns—but means you don’t get access to the raw data.

Measured Data: Reliable and Viable

Measured data gives you an up-close look at movement on arterial streets. It’s collected in the field at the device level, so you can see real-time reports of raw numbers that you have the flexibility to incorporate into your calculations.

The Amount of Data You Collect Matters

Aggregated data can be useful, but it doesn’t hold up when it comes to measuring arterial performance. Because a lot of data is extrapolated, you don’t know how many samples were collected to provide you with the result you’re seeing.

When we break down the probe data displayed in the graph below, we see that a major source of this data came from commercial vehicles. Notice the drop-off between the left-hand and right-hand side of the graph. The right-hand side displays data collected where restrictions were in place that limit the passage of trucks on an HOV-only facility.

Figure 1: I-66 EB in Virginia is in an urban area with high volumes, where restrictions were in place that limit the passage of trucks on an HOV-only facility. The figure illustrates the availability of data over an entire day and shows that commercial vehicles represent a major source of probe data in the National Performance Management Research Data Set.

For arterial performance measures, receiving large amounts of measured data is important because public agencies have different ways of defining how they want performance measures calculated. Measured data is raw and transparent: you can see exactly what was collected at the device level, and you have the flexibility to define and calculate the performance measures you need.

Figure 2: Bluemac x7 provides an unmatched amounts of raw travel time data (as shown in the figure) and processed performance measures. Shown above are travel times observed on Main Street Northbound between 1st Avenue and Lake Elmo Drive in Billings, MT.

Through logging in to a secure portal, customers of the Bluemac x7 have a transparent view of all device-level data in real time. This type of high-resolution data can be used for many types of arterial performance measures:

  • Before/After Studies – Quantifying the change in performance of corridor improvements to validate project expenditures.
  • Performance Monitoring – Understanding performance trends to inform TSM&O activities and/or justify funding needs.
  • Origin-Destination Studies – Understanding the capacity of reroute, or potential for rerouting traffic from a particular location.
  • Trajectory Study – Understanding where vehicles are entering and exiting a study corridor. This helps agencies understand how they should time and operate the traffic signals.
  • Reliability Studies – Understanding how the corridor performs not at one time instance, but rather the range of results. This is useful when trying to determine non-capacity improvements such as incident management strategies and TSM&O solutions.

Each of these studies relies on data that’s not only accurate, but comprehensive enough to tell the whole story. Measured data from Bluetooth devices can give you significantly more data points than probe data (and at a lower cost, too).

Ultimately, good decisions are driven by good data. We understand that every study has a unique goal, and it’s important to us to help our customers take the right path. Don’t hesitate to reach out to talk with one of us about the type of data you need to collect and why; we’d be glad to help.